Method for collecting image data for producing immersive video and method for viewing a space on the basis of the image data

ABSTRACT

A method for collecting image data destined for producing an immersive video, which method comprises a determination of a zone of viewpoints and the set-up of a set of source points situated at end points of the zone of viewpoints, as well as the placement of each time a scanner of a first set of scanners at each of said source points for scanning step by step a space by means of scanning beams and according to a succession of on the one hand azimuth angles and on the other hand elevation angles each situated in a range predetermined by the zone of viewpoints, and determining on the basis of reflected scanning beams image data formed by a distance between the point touched by a beam and the scanner having produced the concerned scanning beam as well as a colour parameter of said touched point and storing them in a memory.

The present invention relates to a method for collecting image datadestined for producing an immersive video, which method comprises asetting up of a first set of at least n (n>1) scanners, each beingprovided for producing scanning beams, which method also comprises thescanning of a predetermined space by each of the scanners of said firstset of scanners by means of scanning beams for producing the image dataof said space, which image data are stored in a memory. She also relatesto a visualisation method of this image data.

Such a method is known from the US patent application 2013/0083173. Sucha method is also used in video games for creating sceneries. To enableto visualise images produced with an immersive video it is necessary tofirst collect image data. This is realised by means of a set of scannerswhich scan a predetermined space which forms the scene in which theimmersive video takes place. The image data thus collected are stored inthe memory.

When the user of a video game wants to move himself in thetri-dimensional scene of the video game he will generally use a keyboardand a computer mouse which executes the video game. The video game willthen calculate in real time the rendering of the 3D scene starting fromthe new viewpoint of the virtual person and this rendering is displayedon the computer screen. This enables the user to move himself in thevirtual world of the video game and to interact with that world.

These simple interactions already enable some users, within a fewminutes of the game, to feel themselves in the skin of the virtualperson of the video game. The virtual immersion sensation consists ingiving the impression to the user of being physically really within thevirtual 3D scene. This sensation can be more or less strong in functionof the appropriateness between what is felt by the user's senses andwhat will be felt if the user was really in the physical equivalent ofthe virtual 3D scene, that is to say in the real world. Systems whichpresents to the user eyes images which are coherent with the rotationmovements of his head are generally called virtual reality systems.

The technique most commonly used for obtaining a virtual reality systemis a virtual reality headset. The user wears the headset on his head,and the headset is connected to the computer. By means of screens and aset of lenses placed before the user's eyes, the headset presents toeach eye synthesis images calculated in real time by the computer. Theheadset also comprises a sensor enabling to measure the orientation ofthe user's head. The principle is the following: the user turns hishead, the virtual reality headset captures this head movement and sendsinformation about the user's new head orientation to the computer, thecomputer produces a stereoscopic rendering of the virtual 3D scene withan orientation of the two virtual cameras corresponding to the neworientation of the user's eyes, the images rendered in real time by thecomputer are displayed in front of the user's eyes.

Different factors will influence the quality of the virtual immersion atvisual level. The principal factor is the appropriateness between theuser's head movement, which is measured by his inner ear, and hisvision. The human being is used to a perfect appropriateness betweenthese two senses in the real world. According to the incoherence rangebetween the images seen by the eyes and the movements felt by the innerear of the user, the latter will feel a slight discomfort sensation, avisual exhausting, headaches, a sickness sensation and stomach reversalwhich could even lead to vomiting. Those effects are called virtualreality sickness or “Cyber-Sickness” and are similar to sea sickness.

The known immersive videos are monoscopic or stereoscopic pre-recordedor pre-calculated movies which cover a vision field of 360 degreesaround the user. Those known immersive videos can be visualised by meansof a virtual reality headset. The virtual reality headset measures theuser's head orientation and enables the computer to send to the headsetdisplay the images for the right and left eye corresponding to thisorientation.

For known immersive videos, as for normal videos, the images arepre-recorded or pre-calculated, they are thus not calculated in realtime. Thus, instead of 1/60 of a second for example for calculating animage in real time, it could have been calculated in more than one hour.This enables to have an image quality which is much better than the oneof virtual reality.

When the user performs a translation movement with his head, his visualfield will be shifted. During such a shift the images of the objectswhich are near to the user will move faster than the images of objectswhich are further away. This effect is clearly observed when one is in amoving train and looks through the window, one sees the close fencesmove very fast, while far away mountains look as if they stay still.This effect is called parallax.

A problem of the known immersive videos is that they do not take intoaccount the translation movements of the head of the user and thus thatthat they cannot provide interactive parallax. This limitation stronglyrestricts the immersive quality of the known immersive videos. Indeed,the user's brain expects to see parallax when his head moves, but doesnot perceive it. This shortcoming reduces the user's vision comfort aswell as the immersive sensation and increases strongly the risk of“Cyber-Sickness”.

It is an object of the invention to realise a method for collectingimage data destined for producing immersive video which enables to takeinto account these movements, in particular the translation movements,of the user's head.

To this purpose a method for collecting image data destined forproducing an immersive video is characterised in that a zone ofviewpoints is determined by delimiting a volume from which a user of theimmersive video will be able to see said space and to perform head amovement, in particular a translation movement, inside the zone ofviewpoints, a second set of m (m>1) source points located at the ends ofthe zone of viewpoints being thereafter determined, which setting up ofsaid first set of at least n scanners being realised by placing at eachof said source points each time one of said scanners of said first set,said scanning of said space being done by means of said scanners placedat said source points and by scanning step by step said space accordingto a succession of at the one hand azimuth angles and on the other handelevation angles each located in a range predetermined by said zone ofviewpoints, which production of image data is performed by collectingfor each produced scanning beam the scanning beam reflected by each timea touched point situated within said space and touched by the concernedscanning beam and by determining by each step and on the basis of thereflected scanning beam a distance between the touched point and thescanner having produced the concerned scanning beam as well as a colourparameter of said touched point, said data being stored in the memory inthe form of a matrix structured according to the azimuth and elevationangles.

By determining a zone of viewpoints which delimits a volume from which auser of the immersive video will be able to see said space and perform amovement with his head inside the viewpoints zone, it will becomepossible to determine the source points where the scanners will beplaced and thus to scan the space as from those source points. This willthen enable to collect image data as from this viewpoint zone and thusto take into account the movements, in particular the translationmovements, of the user's head and to provide inside the headset a viewwith an interactive parallax effect. One speaks about interactiveparallax by opposition to a parallax which could be qualified aspassive, which would be linked to the displacement in an immersive videoof the viewpoint executed by the director of the immersive video.

The virtual reality systems enable to have this interactive parallax,but they have therefor to calculate in real time the images presented tothe user's eyes. This calculation in real time strongly reduces theimage quality.

The method for creating immersive videos with interactive parallaxaccording to the invention uses pre-calculated synthesis images or realshootings, thereby providing a better image quality in comparison to thereal time of virtual reality. The inclusion of the interactive parallaxin immersive videos enables the user to feel a very good immersivesensation, and reduces substantially the risk of cyber-sickness.

The zone of viewpoints enables to limit the quantity of informationwhich has to be stored in order to reproduce the scanned space. Thislimitation of information enables to have a quantity of information anddata which can be managed. The configuration, the dimension and shape,of the zone of viewpoints predetermines the number and set-up of thescanners used for scanning the space.

A first preferred embodiment of the method according to the invention ischaracterised in that the zone of viewpoints is formed by an essentiallyrectangular volume, in particular a rectangular parallelepiped, having aheight of at least 30 cm, a depth of at least 30 cm and a width of atleast 30 cm. This enables to cover the positions which can be reachedduring the translation movements and/or the rotation of the user's head,when the latter maintains the rest of his body in a fixed position.

A second preferred embodiment of the method according to the inventionis characterised in that the stored data are filtered by determining foreach point touched by a scanner if that point can be reached by a beamlaunched by at least one other of said n scanners, and in case where theconsidered touched point can be reached by a beam launched by at leastanother of said n scanners it is determined on the basis of apredetermined selection criteria if the stored data of the consideredtouched point have to be eliminated from the stored data. This filteringstep enables to filter and save only the points which give usefulinformation. This enables to reduce the amount of stored data forproducing immersive video with interactive parallax.

A third preferred embodiment of the method according to the invention ischaracterised in that the selection criteria is based on the area of thesurface scanned between two successive scanning steps according to theazimuth angle and two successive scanning steps according to theelevation angle by the scanner having produced the considered touchedpoint and the single or several scanners among the other n scannersbeing able to reach the considered touched point.

Preferably the method according to the invention is characterised inthat the scanners which are used are either virtual scanners, orphysical scanners. The scene can thus be produced through virtual orphysical scanners, the latter being used in a same manner as directorrecords with his camera the scenes of his movie.

According to another preferred embodiment of the method according to theinvention the zone of viewpoints is shifted in said space from a firstposition towards a second position situated at a predetermined distanceof the first position, the scanning by each of the scanners of saidfirst set of scanners and the production and storage of the image dataof said space being repeated for each second position of the zone ofviewpoints after the one realised for the first position. It is thuspossible to consider the system as creating around the user atvisualisation time a virtual 3D scene for each time fraction of theimmersive video. Each of those ephemeral 3D virtual scenes is limited towhat the user can see from his zone of viewpoints. The evolution of theaspect of those scenes corresponds to the movement of the objects and/orpersons in the video and to the displacement of the position of the zoneof viewpoints controlled by the movie director. Thus, contrary to thevirtual reality where, at the moment of the rendering in real time, acamera is moved in the 3D scene when the user is moving. According tothe invention it is the 3D scene which moves changes around the userwhen the zone of viewpoints has been displaced at the creation of theimmersive movie with interactive parallax.

The visualisation method of immersive videos with interactive parallaxaccording to the invention comprises:

-   -   a) a determination within the zone of viewpoint of a position        and an orientation of the eyes of a user by means of sensors and        the use of an algorithm predicting the head movement of the        user, for determining what will be seen by the user;    -   b) a selection on the basis of the position and orientation of        the eyes of the user of image data among the stored image data        necessary for visualising the part of the space which can be        seen by the user;    -   c) a loading in a temporary memory of the selected image data;    -   d) a production of two images on the basis of the image data        stored in the temporary memory; and    -   e) a presentation to the user's eyes of the two produced images.

This enables to display to the user a density of points loaded as fromimage data which is coherent with the definition of what is displayed ina virtual reality headset.

Preferably the visualisation method according to the invention ischaracterised in that the presentation of two images to the user isperformed by means of a virtual reality headset.

Preferably the visualisation according to the invention is characterisedin that it is used in a device conferring movement to the user, thecoordinates of said conferred movement being sent to a visualisationsystem which applies said visualisation method for synchronising theflow of images with said movements. This enables to couple to thevisualisation according to the invention the movements conferred to theuser.

The immersive video can thus be applied to a “ride” in attraction parks.The principle of a ride is to be embarked, generally in a seat throughdifferent scenery. This comparable to rollercoaster, but the accent ismore put on visiting the sceneries than on the sensation ofacceleration.

The present invention will now be described in more details by means ofthe drawings showing a preferred embodiment of the method according tothe invention. In the drawings:

FIG. 1 illustrates a volume representing a zone of viewpoints in which auser can move his head;

FIG. 2a illustrates a scene and FIG. 2b the visible part of the scenescanned with respect to the zone of viewpoints;

FIG. 3 illustrates a precision concept of the space scanned with respectto the zone of viewpoints;

FIGS. 4a and 4b illustrate the position of the first set of at least nscanners in the predefined zone of viewpoints;

FIGS. 5a and 5b illustrate the points touched in the space scanned byeach time a scanning beam emitted by a scanner;

FIG. 6 illustrates the concept of a point in space which can be reachedby two different scanners;

FIG. 7 illustrates the scanning of a scene and the filtering the touchedpoints;

FIGS. 8a and 8b illustrate a method for filtering by apparent surface;

FIGS. 9a to d illustrate the filtering method granting a priority to thescanners;

FIG. 10 illustrates the sampling by means of other scanning beams of aspace having objects situated a different distance with respect to thecentral point of the scanner;

FIG. 11 illustrates a relation concept between the maximum and minimumdistance of the other touched points and the perception by the user asfrom a viewpoint shifted with respect to the scanner;

FIG. 12 illustrates that a density of touched points is coherent withthe angular definition of the display;

FIG. 13 illustrates the ecospheric representation of a scanning and thestorage related thereto;

FIG. 14 illustrates the concept of the transfer of the zone ofviewpoints;

FIG. 15 illustrates the storage of image data in the memory; and

FIG. 16 illustrates the concept of modifying the reflected beam.

In the drawings, a same reference sign has been allotted to a same oranalogous element.

Computer programs can simulate the equivalent of a complete movie studioincluding the scenery, the lighting and the cameras. Here, we speakabout tri-dimensional objects, virtual light and cameras, those elementsdo not exist in the real physical world, they only exist as a simulatedrepresentation in a computer. An example of a computer program of thistype is the “Maya” software of the company “Autodesk”. The set of thosevirtual tri-dimensional elements, for example formed by objects, lightand a camera, is called virtual 3D scene, or more simply the 3D scene orvirtual 3D space.

Once the virtual 3D space is put in place, the computer can calculatethe image corresponding to what is seen by the virtual camera in thevirtual 3D space and this taking into account the objects and lightingpresent in that 3D space and the position of the virtual camera. Thiscalculation is called 3D virtual space rendering and the resulting imageof this rendering is a synthesis image.

Both eyes of a user see the physical real world according to twoviewpoints which are slightly different, they are spaced apart onaverage by 6.5 cm for an adult person. This distance is calledinterocular distance. This small shift of the viewpoint on a same realscene, enables the brain of the user to define at which distance theobjects around him are located. A stereoscopic movie consists inrendering two different images of a same scene for each eye of the userin order to produce the depth effect.

The rendering software can take into account the movements of objectspresent in the space and the luminosity thereof. If then the software isrequested to furnish successive renderings at different moments in time,the rendered images will be different and a movie with synthesis imageswill be obtained. In the framework of the traditional movie, a second ofan action is decomposed in twenty-four fixed images, and thus forcreating a movie in synthesis images for a presentation in a movietheatre, it will be necessary to calculate twenty-four images per secondfor an action in a movie.

One speaks about pre-calculated synthesis images when the differentimages of the movie are first rendered and stored, and then played laterat a pace corresponding with the diffusion media of for exampletwenty-four images per second for a traditional movie. The calculationof each synthesis image can take a lot of time for obtaining a goodimage quality. In most cases, the rendering takes more than one hour perimage. Thus, it is typical that a computer calculates during a whole daylong (twenty-four times one hour) the equivalent of one second of themovie (twenty-four images per second).

If the computer is capable to render each image at the same pace thanthe pace used to display the images, one then speaks about that therendering is computed in real time. Again, in the example of the moviewith twenty-four images per second, in order to render the movie in realtime, this implies that each image is calculated in 1/24^(th) of asecond at the maximum.

The sensation of virtual immersion consists in giving the impression tothe user of being really physically inside the virtual 3D space. Thissensation can be more or less strong in function of the adequacy betweenwhat is sensed by the senses of the user and what would be sensed if theuser was really in the physical equivalent of the virtual 3D space.

Systems which present to the user's eyes images which are coherent withthe rotation movements of the user's head are generally called Virtualreality systems.

The most commonly used technique for obtaining a virtual reality systemis a virtual reality headset. The user wears the headset on his head andthe headset is connected to a computer. The headset presents, by meansof displays and a set of lenses placed before the user's eyes, to eacheye synthesis images calculated in real time by the computer. Theheadset also comprises a sensor enabling to measure the orientation ofthe user's head. Use is also made of algorithms which enable to predictthe movements of the user's head.

The principle is the following, when the user turns his head, thevirtual reality headset perceives this movement of the head and sendsthe information about the new orientation of the user's head to thecomputer. The computer makes a stereoscopic rendering of the virtual 3Dscene with an orientation of the two virtual cameras corresponding tothe new orientation of the user's head. The images rendered in real timeby the computer are displayed before the user's eyes.

It should be noted that the modern virtual reality headsets, such as theone made by the company “Oculus”, enable to take into account not onlythe orientation of the user's head, but also his position.

Different factors will influence the quality of the immersive experienceat the visual level. The principal factor is the adequacy between themovement of the user's head measured by his inner ear and his vision. Inreality the user is used to a perfect adequacy between these two senses.In function of the level of incoherency between the images seen by theeyes and the movements felt by the inner ear of the user, the latterwill feel a slight feeling of being uncomfortable, a visual tired,headaches, a feeling of disease and a stomach return which could lead tovomiting. Those effects are called the “virtual reality sickness” or“Cyber-sickness” and can be compared to being sea-sick.

While recording a scene, which takes place in a space, a classicalcamera records the action taking place just in front of it and on thesides up to the limit of the field of vision. This field of vision isexpressed in degrees and provides the total vision angle covered by thecamera.

In the particular case of spherical video, the field of vision of thecamera is of 360° horizontally and 180° vertically, the field of visionis thus total as the camera can see in all directions.

A stereoscopic spherical video couples the characteristics of thespherical video and the stereoscopic video. It thus concerns a videocouple, the one provided to the right eye and the other one for the lefteye. Each of those two videos covers the complete spherical field ofvision.

By coupling a virtual reality headset with a stereoscopic sphericalvideo, one obtains a known immersive video system. The virtual realityheadset measures the orientation of the user's head and transmits it tothe computer. The computer extracts from each of two stereoscopicspherical videos the part of the video which corresponds to the field ofvision of the new orientation of the user's head. Those two pieces ofvideo are displayed before the user's eyes.

These known immersive videos present certain immersive characteristics,for example a certain adequacy between the rotation movements of thehead felt by the inner ear and the images reaching the user's eyes, anda certain perception of depth of the scenes presented to the user. Butthese known immersive videos are taken from a unique viewpoint, they donot enable to take into account the translation movements of the user'shead, which considerably reduces the immersion sensation and above allsubstantially increases the chances of “cyber-sickness”.

Before the invention, the two methods enabling to obtain an immersionsensation in a video were on the one hand the virtual reality, which cantake movements into account, in particular a translation, of the user'shead, and thus create a good immersion sensation, but implies tocalculate the images in real time which considerably reduces the imagequality, and on the other hand the known immersive videos, which do notprovide good immersion sensations and induce a high risk of“cyber-sickness”.

The invention enables to take into account the shifting of the user'shead 1 in a restricted volume which is called zone of viewpoints (ZVP)and which is illustrated in FIG. 1. The zone of viewpoints ZVP isdetermined by delimiting a volume from which a user 1 of the immersivevideo will be able to see the space 3 in which the scene takes place andperform with his head a translation and bending movement inside thiszone of viewpoints. In practice the size of zone of viewpoint ZVPcorresponds preferably to the latitude of the head movement which theuser 1 has naturally around his position when at rest, while the userdoes not move the rest of his body. This rest position correspondspreferably to the position of the user's head 1 when he stands right andrelax, without bending neither stand up or sit down. The latitude of themovement corresponds to the positions which can normally be reached bythe user's head without doing a step, in the case of a standingposition, and without standing up, neither displacing his chair, in thecase of a sitting position. The exact size of the zone of viewpoints ZVPand its geometrical shape, can change in function of the positionforeseen by the user 1. He can be either sitting down, laying down, orstand right.

The zone of viewpoints is for example formed by an essentiallyrectangular volume, in particular a rectangular parallelepiped, having aheight of at least 30 cm, in particular 50 cm, a depth of at least 30cm, in particular of 1 m, and a width of at least 30 cm, in particular 1m. Such a dimension of the zone of viewpoints is sufficient fordelimiting the potential positions of the head, and thus of the eyes, ofthe user 1. The point R is the central point of the zone of viewpointsZVP, that is to say the point situated between the eyes of the user 1when he is at a rest position. According to another embodiment the zoneof viewpoints is formed by a volume having an essentially octahedronconfiguration.

By scanning the space as from the zone of viewpoints ZVP having theshape of a parallelepiped which measures for example 105 cm in depth and45 cm in height, with a range of 15 cm covered by a scanner, one willuse a total of 8×8×4=256 scanners.

Care has to be taken that the zone of viewpoints ZVP presents asufficient size but not too large. An infinite size of the zone ofviewpoints would correspond to be in a standard virtual reality mode.This zone of viewpoints ZVP thus enables to limit the quantity of imagedata which will be stored in order to limit the storage capacity and tomake them manageable in comparison with virtual reality systems whichneed to store tremendous quantity of information for obtaining a detaillevel equivalent to the one obtained by the method according to theinvention.

FIG. 2 illustrates a comparison between the information present at ascene 10 of virtual reality and a scene 10A of an immersive video withparallax according to the invention. The scene 10 in virtual reality inwhich the user can be located, is complete. That is to say, when theuser is moving within the scene 10, the set of objects of the virtualscene are loaded into the scene. While, according to the invention, onlythe elements which are potentially visible as from the zone ofviewpoints ZVP are loaded at a given moment. In FIG. 2b the more thickerlines of the scene 10A show the part of the elements of the scene whichare potentially visible as from the zone of viewpoints ZVP. Thus, onlythe left side of the rectangular shape is visible, while the right sideof the scene circumference 10 a is not visible as from the predeterminedzone of viewpoints ZVP. This enables to reduce the number of pointstouched by the scanner beams and thus enables to reduce the need ofmemory capacity for recording the information of the touched points.

FIG. 3 illustrates the concept of precision of points touched in spaceby a scanner beam emitted by a scanner. Always in the example of thescene 10, in virtual reality, the precision of the modelling of thevirtual objects in the virtual scene is homogeneous. That is to say thatthe precision in the details of the models will be the same for all theobjects 11 and 12 in the virtual scene. In the case of the invention,the objects 11 close of the zone of viewpoints ZVP present much moreprecision than the objects 12 which are far away. Thus, the points Ptouched by a scanner beam and which are close to the object 11 presentmore touched points resulting from the scanning than the points P′touched of the object 12 far away. According to the example of FIG. 3,the touched points P of the close object 11 present nine points, whilethe touched points P′ of the object 12 faraway present only threepoints. Thus, the precision is variable in function of the position ofthe zone of viewpoints ZVP, the precision of a same object can be verylarge at one moment in the immersive movie and very weak at anothermoment. Just like in nature, the objects which are close to the zone ofviewpoints ZVP present a good resolution and the objects far away a lessgood resolution, everything thus depend of the distance between theobject and the zone of viewpoints ZVP.

As illustrated in FIG. 4a , for collecting image data destined forproducing the immersive video, the method according to the inventioncomprises the set-up of a first set of at least n scanners S₁, s₂, . . .s_(n) (n>1), each provided for producing scanning beams r₁, . . .r_(j−1), r_(j) (j≥J). The minimal number J of scanning beams isdetermined in function of the resolution of the display screen foreseenfor the visualisation. Preferably the scanning step, that is to say theangle between two subsequent beams (r_(j)-r_(j+1)) is lower or equal tothe angular resolution of the display. For clarity reasons, only for oneof the scanners the scanning beams are represented in the drawing. Eachof the scanners s_(i) (1≤i≤n) of the first set is used to scan, by meansof the scanning beams, the space 3 for producing image data of thatspace, which image data are thereafter stored in a memory.

In order to set up the scanners of the first set of at least n scanners,a second set of m (m>1) source points C1, C2, . . . , C7 and C8 situatedat end points of the zone of viewpoints ZVP is determined. The number ofeight source points shown in the FIG. 4a is linked to the rectangularshape of the zone of viewpoints and is only given as an example and doesin no way limit the scope of the invention. The set-up of at least nscanners is realised by placing at each source point each time one ofsaid scanners of the first set.

In order to scan the space with a sufficient definition the scanners areplaced at the end points of the zone of viewpoints. Of course, it ispossible to determine supplementary source points in the zone ofviewpoints. FIG. 4b illustrates a configuration where the zone ofviewpoints is provided with a grid. This grid is preferably applied oneach of the faces. The different points of this grid can form sourcepoints C_(k) destined for placing a scanner thereon. It is also possibleto have source points inside the zone of viewpoints. The number ofsource points used at the end points of the zone of viewpoints ispreponderant. The placing of supplementary source points at the surfaceof the zone of viewpoints can improve the quality of the sensationsduring the viewing. On the contrary, the increase of supplementarysource points inside the zone of viewpoints has not much interest.

The term scanner is used in the description of the invention for a setof virtual or physical 3D scanners, which preferably realise a scanningin all directions, at 360 degrees.

The scanning of the space is realised by means of scanners s_(i) placedat the source points C by scanning step by step said space according toa succession of on the one hand azimuth angles, and on the other handelevation angles each within a range predetermined by the zone ofviewpoints. Preferably the scanning steps have an angle value situatedbetween 0.01° and 1°, more particularly between 0.025° and 0.1°. Theproduction of image data is realised by collecting for each scanningbeam n (1≤j≤J) produced, the scanning beam reflected by each time atouched point P (see FIGS. 5a and b ), situated within said space 3 andtouched by the concerned scanning beam r₁. Based on the reflectedscanning beam a distance (d) between the touched point P and the scanners having produced the corresponding scanning beam r₁ is also determinedat each step, as well as a colour parameter of said touched point. Thus,for each touched point P the distance d is obtained between that point Pand a point, for example the central point, of the considered scanner.As the direction of each scanning beam is known and the distance d tothe point P is calculated, the tri-dimensional position of the point Pin the scanned space can be reconstructed.

The colour of the touched point P is for example calculated in the usualway for synthesis images as if the scanning beam was a vision beam of avirtual camera. The computer will thus take into account for calculatingthe colour of the touched point P the texture and the appearance of thetouched object, the virtual light in the space 3 and their reflection aswell as the position of the spherical virtual camera.

After having determined the distance d of the point P and its colour,these values are stored in the memory as image data. The storage ispreferably done in the form of a matrix structured according to theazimuth and elevation angles. Each matrix element corresponds to theangle of the scanning beam. This is illustrated in FIG. 15 where thelines of the matrix each time show a scanning step according to anelevation angle and the columns of the matrix each time show a scanningstep according to the azimuth angle. A stored value V_(rc) at line r andcolumn c represents thus the distance d and the colour obtained by thescanning beam having the elevation angle equal to the value of thescanning step according to the elevation angle multiplied by the valueof the number r of the line and by the scanning beam having an azimuthangle equal to the value of the scanning step according to the azimuthmultiplied by the value of the number c.

As the case may be, it is also possible to store in the memory thevector of the normal of the touched surface.

This matrix structure enables to store the data in the same manner asthe one according to which the scanning takes place and thus to maketheir addressing easier.

The fact of using a second set of source points and at least n scannerswill have as consequence that a same point in space will be reached bymore than one scanner.

In the method according to the invention, only the information of thetouched points which is useful for representing the scene from the zoneof viewpoints ZVP is preferably maintained in the memory. To this endfor each point touched by a scanner it is determined if that point canbe reached by a beam launched by at least one other of said n scanners.This concept is illustrated in FIG. 6 which shows two scanners s₁ and s₂respectively placed at the source points C₁ and C₂ . The scanning beamsr of scanner s₁ can reach the point P. Point P is now considered asbeing a source point at which a fictive scanner s_(f) is placed and itis verified if a beam r_(f) of that fictive scanner s_(f) can reach thesource point C₂ where scanner s₂ is placed. If this is the case, one canconsider that point P as being reachable by scanner s₂. In the casewhere the considered touched point can be reached by a beam launched byat least one of the other n scanners it is determined on the basis of apredetermined selection criterion if the stored data of the consideredtouched point has to be eliminated from the stored data. The object ofthis filtering is to avoid redundant image data are stored in thememory.

FIG. 7 shows the scanning of a scene with respect to two scanners s₁ ands₂ placed at respective source points C₁ and C₂. A first set 4 oftouched points is obtained when the space 3 is scanned with scanner s₁.A second set 5 of touched points is obtained when scanning the space 3with scanner s₂. The first and second set 4, 5 of touched points aredifferent. The scanner s₁ can only reach the horizontal part of thescene in rectangular shape, while the scanner s₂ can reach the samehorizontal zone as the scanner s₁ and also the vertical side of thescene at the right in the figure.

After having obtained the first and second set of touched points 4, 5, afiltering of those different touched points has thereafter to beapplied. The touched points shown under 6 in FIG. 7 illustrate the mixof points 4 and 5 touched by the scanner s₁ and by the scanner s₂. Itcan thus be seen that within the points 6 the points of the horizontalpart are doubled and that a filtering can take place. This filteringwill then consist in eliminating the touched points of the horizontalpart obtained by scanner s₂. Only the points shown under 8 will bemaintained in the memory.

In order to proceed with the filtering the selection criterion ispreferably based on the area of the surface scanned between twosuccessive scanning steps according to an azimuth angle and twosuccessive scanning steps according to an elevation angle by the scannerhaving produced the considered touched point and the single or severalscanners among the n other scanners which could reach the consideredtouched point.

This concept of scanned surface area is illustrated in FIG. 8a . In thisfigure, the beams r_(a1) and r_(a2), respectively r_(e1) and r_(e2)represent successive scanning beams according to the azimuth angle,respectively the elevation angle.

The surface is delimited on the one hand by the points touched by thebeams r_(a1) and r_(a2), and on the other hand by the points touched bythe beams r_(e1) and r_(e2), and form the scanned surface area betweentwo successive scanning steps. When this scanned surface area isdetermined, it becomes possible to verify if one or more other of the nscanners of the first set of scanners can also reach this scannedsurface. When this or these other scanners have been identified, itbecomes possible to select among the data obtained while scanning bythese other scanners the one to be eliminated.

According to another embodiment illustrated in FIG. 8b , the filteringis realised in that an angle (β) between the normal N on the scannedsurface and the scanning beam having produced the touched point P isdetermined. As the scanning step has an angle of low value the distanced of the touched point P with respect to the scanner s will not vary alot between two subsequent scanning beams. One can thus use thisdistance d as a parameter for determining the area of the scannedsurface. This area will then be proportional to the square of thedistance (d) divided by the cosines of the angle β and the thus obtainedvalue of this area can form the selection criteria. On the basis of thelatter selection criteria only the data stored which is linked with thevalue having the smallest area of the scanned surface will be kept inmemory. The idea consists in maintaining the touched point representingmost of the details, and thus the one which represents the smallestscanned surface area.

It should be noted that the latter embodiment can be used for comparingthe apparent surfaces of a same point between different scanners if theyhave the same angular definition.

The selection criteria can also be based on the distance between thetouched point and the scanner having produced the touched point and thedistance between the touched point and the single or several scannersamong the n other scanners which can reach the touched point. The savedstored data being the one corresponding to the scanner having caused thesmallest distance.

It is also possible to attribute beforehand a priority order to each ofthe n scanners placed on the source points, the selection criteria beingbased on this priority order. This filtering method is illustrated inFIG. 9. Use is made of an algorithm for each scanned point in order toverify if the scanned point P is visible from a scanner having a higherpriority. If this is the case, the scanner having a higher priority willrecord the point. If not, it will be the running scanner which willrecord the point.

In FIG. 9a three scanners are showed noted s₁, s₂, and s₃. Forsimplifying the representation is made in two dimensions. The priorityorder of the scanners is equal to their number. Thus, the scanner s₁ haspriority over s₂, which has priority over scanner s₃. The FIG. 9b showsthe surfaces which will be kept for the scanner s₁. As it has priorityover the other, it keeps all the surfaces it can see. The FIG. 9c showsthe surfaces which will be kept for the scanner s₂. The scanner s₂ seestwo zones which are not visible for the scanner s₁. The FIG. 9d showsthe surfaces which will be kept for the scanner s₃. Those are the onlysurfaces which will be kept in the for the scanner s₃, indeed, the restof the surfaces which the scanner s₃ can see have already been seen bythe scanners s₁ or s₂ which have a higher priority.

Certain apparent colour components of a point on an object will dependof the position of the camera, which position will influence theincident angle of the scanning beam on the scanned object. Thiscomponent is called in synthesis images the specular part of therendering. In order to explain this in a simple manner, this part isequivalent to a reflection of a scanning beam.

The same point on a same virtual object with a same light will not havethe same appearance for two different positions of the virtual camerabecause of this reflection component.

This concept is illustrated in FIG. 16 which shows a space 3 whichcomprises for example a reflective wall 15 like a mirror. A scanner s₁is placed in front of this wall and launches a scanning beam r_(j)towards this wall. As this wall is reflecting, the scanning beam r_(j)will be reflected by this wall according to a same angle as the incidentangle on the wall and this reflection will produce a scanning beamr_(j′) which will touch object 16 which is on its passage. This will onits turn cause a reflexion of the scanning beam r₁ by this object. Thelatter will then reach the wall 15 as from which it will be reflectedtowards the scanner s₁. The latter will thus consider the latterreflected beam as coming from point P on the wall 15 and not as comingfrom the object 16. It is thus the colour of the object 16 which will beconsidered by the scanner s₁ as being the one of the point P.

In such a case of objects with important specular or simply highlyreflecting material, there is thus a risk to have incoherence by placingside by side two points which have been taken from two differentscanners, placed at different positions.

Preferably, use is made of a rendering technique for calculating coloursof points which “cheats” on calculating the direction of the scanningbeam.

The used method consists while calculating the colour of a touched pointP to give for calculation of the beam reflected by the surface 15, notthe real direction of the scanning beam launched by the scanner whichcalculates that point P, but a beam for which the direction wouldcorrespond to the one of a beam launched from a source point K,preferably placed at the centre of the zone of viewpoints ZVP. Thus, allreflections and specular will be coherent, for a same touched point P,whatever be the position of the recording 3D scanner.

In pre-calculated synthesis images, the colour of a pixel is generallynot calculated on the basis of a single beam launch, but rather on aplurality of beams in the pixel surface. Each launched beam for a pixelcorresponds to a sample for determining the colour of the pixel. Themulti sampling consists thus in launching several beams for a same pixeland to make a weighted average of the colours obtained for each beam inorder to determine the final colour of the pixel. The fact of raisingthe number of samples for a pixel increases substantially the quality ofthe rendering in particular in situations where the pixel corresponds tothe border of an object.

In a similar manner, for calculating the colour of a touched point P ina direction, it is possible to improve the quality of the rendering bymultiplying the scanning beams inside a same scanning step. FIG. 10illustrates how by means of four other scanning beams originating from ascanner s and situated inside of a same scanning step, one can determineother touched points P1, P2, P3 and P4 in space. The colours and thedistances d of the four other touched points thus obtained by the fourother scanning beams could be averaged. But, in the case of recordingdistances, this averaging poses a problem. Indeed, the different otherscanning beams can touch objects 16 and 17 at different distances.

If the distances are averaged, one obtains in this case distances whichdo not correspond to any surface in the scanned space. The problem isthat viewed from a somewhat different viewpoint, these averaged pointswill pose a problem as they will appear as hanging in the void. Thispoint suspended in the void is marked with an x in FIG. 10. According tothe example shown in FIGS. 10, P1 and P2 are two scanned points of anobject 16 having a blue colour. P3 and P4 are two scanned points of anobject 17 having a red colour. Thus, the colour of point x, ifdetermined by simply making an average of the other touched points P1,P2, P3 and P4 will be purple and its position the average position ofthe points p1, P2, P3 and P4. When that point x is viewed from a cameraplaced at source point C, this will not cause a problem. From anotherviewpoint D, the point x will not correspond to an existing geometry inthe scanned space and that point x will appear as floating in the air.

One can of course just store the image data of all those other touchedpoints but finally this corresponds to increase the resolution of thescanner and thus to increase the quantity of stored data.

Preferably use is made of a method which enables to correctly aggregatea plurality of other touched points which, once averaged with respect totheir distance, do not create points floating in the air. This preferredvariation consists in employing a method called “Clustering”, whichgroups the other touched points in different groups which are spatiallycoherent. If an average is then made over the distance of the othertouched points of a same group, a spatial position is obtained which iscoherent with the existing geometry in the scanned space.

Several methods of “clustering” which are commonly used in the frameworkof artificial intelligence are possible, such as for example the methodcalled “k-means”.

Finally, one, two or three groups of other touched points are obtained,and the colour of these other touched points within this group can beaveraged, as well as their depth without having problems of pointsfloating in the air.

Starting from the other touched points obtained by the other scanningbeams, a set of distances is determined comprising for each othertouched point the distance between that other touched point and thescanner. Thereafter the minimum distance and the maximum distance issearched among the distances of said set of distances.

This is for example illustrated in FIG. 11. As far as the user at themoment of visualisation will stay in the zone of viewpoints ZVP, thedifference between the maximum distance which is possible between theviewpoint of the user and the centre of each scanner can be calculated,calling this distance ΔZVP (delta viewpoint). In FIG. 11 it should benoted that the scanner centre is C, V the position of the most far awayviewpoint possible in the vision zone with respect to the scannercentre, ΔZVP being the distance between C and V. dmax corresponding tothe distance with respect to C of the other touched point the furthestaway: Pmax, dmin corresponding to the distance with respect to C of theother most close touched point Pmin, αmin corresponds to the angleformed between the strait line going from point V to point C and thestrait line going from V to point Pmin, αmax being the angle formedbetween the strait line going from point V to point C and the line goingfrom V to point Pmax, Δα being the angle difference between αmax andαmin. It is then possible to calculate: αmin=arctan (dmin/ΔZVP),αmax=arctan (dmax/ΔZVP), and Δα=αmax−αmin.

If the other touched points are situated in a range of distances withrespect to point C leading to a value Δα which would be inferior to halfof the angular definition of the display, the splitting into groups ofother touched points is not necessary. Indeed, in such a case, thedistance difference will not be perceived from any point of the zone ofviewpoints and a weighted average of the calculated value of those othertouched points will be determined and this weighed average will besubstituted to the value of the stored image data for the point touchedat the considered scanning step.

If on the other hand such a separation in groups is necessary there is aseparation in different groups on the basis of the position of saidother touched points and one chooses according to a predeterminedcriterion a group among those groups, the point touched at theconsidered scanning step being determined by a weighted average of thecalculated values for those other touched points in the selected group.

The general principle is that a gap of 5 cm in depth at a distance of 1Km will not be distinguished from any viewpoint inside the zone ofviewpoints, on the contrary a gap of 5 cm at a distance of 50 cm will behighly perceived.

A selection criterion for the group of other touched points can beeither the number of points of which the group is constituted or itsaverage distance with respect to the centre of the scanner.

For creating the equivalent of a camera movement in the immersive videoaccording to the invention, the zone of viewpoints is preferably movedin space as from a first initial position towards at least a secondposition situated at a predetermined distance of this first position.The scanning by each of the scanners of the first set of scanners andthe production and storage of image data of the space being repeated foreach second position of the zone of viewpoints after the one performedfor the first position.

A characteristic of the invention is that the density of touched pointsis coherent with the angular resolution of the display, as illustratedin FIG. 12. A surface 51 far away from the zone of viewpoints ZVPpresents only three touched points, while a closer surface 52 presentsat least five time more touched points. The density of touched pointsfor a remote surface is low and the different touched points are atquite a distance from each other. The density of touched points on acloser surface is much higher, and thus better defined. This is coherentwith the display definition when visualising an immersive movie withinteractive parallax according to the invention.

The visualisation of the immersive video with interactive parallaxaccording to the invention, comprises the following steps:

-   -   a) a determination within the zone of viewpoint of a position        and an orientation of the eyes of a user by means of sensors and        the use of predictive algorithms of the head movement of the        user, for determining what will be seen by the user;    -   b) a selection on the basis of the position and orientation of        the eyes of the user of image data among the stored image data        necessary for visualising the part of the space which can be        seen by the user;    -   c) a loading in a temporary memory of the selected image data;    -   d) a production of two images on the basis of the image data        stored in the temporary memory; and a display to the user's eyes        of the two produced images.

The user, having a restricted vision field can at a given moment onlysee a part of the scanned space encoded by the image data.

Preferably, the scanned space is stored under a form which separates inslices the touched points. Each slice corresponds to a slice of thescanning directions. For example, a slice can encode the points seen bydifferent scanners corresponding to azimuth angles of 0 to 45 degreesand elevation angles from 90 to 125 degrees.

A lot of methods have been studied and can be used for displaying thetouched points. We can for example mention: Gaël Guennebaud, LoïcBarthe, Mathias Paulin: Interpolatory Refinement for Real-TimeProcessing of Point-Base Geometry, published in Eurographics 2005,Dublin, Ireland, vol 24, N°3.

Preferably the rendering of touched points is not lighted again, thecolours encoded in the points are directly the one which will bepresented to the user, there is no re-lighting at the time ofvisualisation.

Preferably, the scanning of the points is ecospheric, that is to saythat it is adapted in function of the elevation angle as illustrated inFIG. 13. The points at the poles of a sphere are not scanned with thesame azimuth angle step as the one on the equator, and this in order toavoid redundant points and thus limit the number of points to scan. Thescanning with the smallest azimuth angle step will be realised at theequator, while at the other latitudes the scanning will have a higherazimuth angle step. The ecospheric method keeps the principle ofencoding the latitude in the ordinate of the storage matrix, and thelongitude in the abscise of the storage matrix, just as for theequirectangular encoding, but the ratio between azimuth and abscise isno longer linear.

Thus, one calculates for each scanned line (each elevation), theequivalent circumference of the circle which is represented by thatline. Just as a line of the storage matrix represents a horizontalcross-section of the sphere, this will provide a circle on thehorizontal plane cross-section.

This circumference is thus, on the basis of a sphere with a radius 1 ofsin (α)*2*PI. With an elevation angle a starting from the North pole,that is to say at the North pole α=0 degrees, at the equator α=90degrees and at the South pole α=180 degrees, the ratio of thiscircumference with the circumference at the equator is thus simply sin(α).

All points on a same line are at a same distance from each othercorresponding to on angle increment of Δβ . . . But this angle incrementΔβ varies from line to line, again relative to sin (α). According to theformula Δβ=360 degrees/(number of columns of the storage matrixmultiplied by sin (α)). It should be noted that all the columns of thestorage matrix are only used at the equator, all the other latitudes useless columns.

The ecospheric method enables to have a good homogeneity of the surfacescorresponding to each touched point in space and covers completely allthe scanning directions.

At FIG. 13 a slice of the corresponding sphere at all the longitudes isshown for a latitude α=45° corresponding to circle 26. The circle 25 isa slice of the sphere corresponding to all the longitudes for a latitudecorresponding to equator (α=90 degrees). The projection 40 is a circleseen from above and corresponding to a latitude of the equator, itsradius is by definition 1 and its circumference is of 2π, the projection50 is a circle seen from above at a latitude α=45°, its radius R is ofsin (α) and its circumference of 2π* sin(α). W is the centre of thesphere, M is the corresponding ecospheric storage matrix. The line 90 isthe stroke of touched points corresponding to a latitude α=45°. One willobserve that not all the columns of the matrix M are taken into account,indeed only a number of columns defined by the total number of columnsof M multiplied by sin (α) is considered. The line 100 is the stroke oftouched points corresponding to a latitude of the equator, it takes allthe columns of the matrix M.

The zone of viewpoints ZVP can be shifted by the video director justlike he would move a camera with a unique viewpoint, as illustrated inFIG. 16. Thus, contrary to virtual reality where, at the moment ofrendering in real time, a camera is moved in a virtual space when theuser is moving. According to the invention it is the space 3 which movesaround the user 1 when the zone of viewpoints ZVP has been shifted whilecreating the immersive movie.

One can think of the system as recreating around the user 1 at themoment of visualisation, a virtual 3D scene for each time fraction ofthe immersive video. Each of the virtual ephemeric scenes is limited towhat the user 1 can see as from the predetermined zone of viewpointsZVP. The evolution of the aspect of those scenes corresponds to themovement of the objects or persons in the video and to the movement ofthe position of the zone of viewpoints controlled by the movie director.

Thus, in FIG. 14 a scene 3 is scanned from a first position of the zoneof viewpoints ZVP at a first time t₁, and thereafter it is again scannedas from a second position in the zone of viewpoints at a second time t₂.Thus, at t1 a first set of touched points 9 is obtained, and thereafterat t2 a second set of touched points 9′ is obtained. For the user 1 itis the scene which has been moved.

At visualisation, it is of interest to be able to mix synthesis imagesin real time with images generated according to the invention. Thus, onecan for example add an avatar formed by the user's body, or avatars ofother user's bodies which are or not physically present. It is alsopossible to add informative elements such as text or schemes in functionof the direction at which the user looks, or game elements, such asdynamic targets. One can also add static or dynamic advertising.

Upon reading the immersive video according to the invention, the usercan be put on a system recreating acceleration sensations therebyconferring a movement to the user.

The visualisation can also be improved by a sound immersion enabling tohave a sound in three dimensions with for example classical techniquessuch as Ambisonic, HRTF (Head Related Transfer Function) and Binaural.

1.-15. (canceled)
 16. A method for collecting image data destined forproducing an immersive video, which method comprises a setting up of afirst set of at least n (n>1) scanners, each being provided forproducing scanning beams, which method also comprises the scanning of apredetermined space by each of the scanners of said first set ofscanners by means of scanning beams for producing the image data of saidspace, which image data are stored in a memory, characterized in that azone of viewpoints is determined by delimiting a volume from which auser of the immersive video will be able to see said space and toperform with his head a movement, in particular a translation movement,inside the zone of viewpoints, a second set of m (m>1) source pointslocated at the ends of the zone of viewpoints being thereafterdetermined, which setting up of said first set of at least n scannersbeing realized by placing at each of said source points each time one ofsaid scanners of said first set, said scanning of said space beingrealized by means of said scanners placed at said source points and byscanning step by step said space according to a succession of at the onehand azimuth angles and on the other hand elevation angles each locatedin a range predetermined by said zone of viewpoints, which production ofimage data is realized by collecting for each produced scanning beam thescanning beam reflected by each time a touched point situated withinsaid space and touched by the concerned scanning beam and by determiningby each step and on the basis of the reflected scanning beam a distance(d) between the touched point and the scanner having produced theconcerned scanning beam as well as a color parameter of said touchedpoint, said data being stored in the memory in the form of a matrixstructured according to the azimuth and elevation angles.
 17. The methodaccording to claim 16, characterized in that the zone of viewpoints isformed by an essentially rectangular volume, in particular a rectangularparallelepiped, having a height of at least 30 cm, a depth of at least30 cm and a width of at least 30 cm.
 18. The method according to claim16, characterized in that the zone of viewpoints is formed by a volumeessentially octahedron shaped.
 19. The method according to claim 16,characterized in that the stored data are filtered by determining foreach point touched by a scanner if that point can be reached by a beamlaunched by at least one other of said n scanners, and in case where theconsidered touched point can be reached by a beam launched by at leastanother of said n scanners it is determined on the basis of apredetermined selection criteria if the stored data of the consideredtouched point have to be eliminated from the stored data.
 20. The methodaccording to claim 19, characterized in that said selection criteria isbased on the area of the surface scanned between two successive scanningsteps according to the azimuth angle and two successive scanning stepsaccording to the elevation angle by the scanner having produced theconsidered touched point and the single or several scanners among theother scanners being able to reach the considered touched point.
 21. Themethod according to claim 20, characterized in that an angle (β) betweena line perpendicular to the scanned surface and the scanning beam havingproduced the touched point is determined, the surface area beingdetermined on the basis of the square of the distance (d) divided by thecosines of the angle β and forms the selection criteria, and wherein thedata stored with the value having the smallest scanned area is kept. 22.The method according to claim 19, characterized in that the selectioncriteria is based on the distance between the touched point and thescanner having produced the touched point and the distance between thetouched point and the single or several scanners among the n otherscanners being able to reach the touched point, the saved stored databeing the one of the scanner having provided the smallest distance. 23.The method according to claim 19, characterized in that a priority orderis established beforehand for each of the n scanners placed on the pointsources, the selection criteria being based on said priority order. 24.The method according to claim 16, characterized in that scanners whichare used are either virtual scanners, or physical scanners.
 25. Themethod according to claim 16, characterized in that the azimuth scanningsteps are adapted in function of the elevation angle.
 26. The methodaccording to claim 16, characterized in that inside a same scanning stepseveral other scanning beams are produced and other touched points aredetermined by means of said other scanning beams, thereafter there beingdetermined a set of distances comprising for each other touched pointthe distance between that other touched point and the scanner, a minimumand a maximum distance are searched among those distances of said set ofdistances, and on the basis of a criteria depending of that minimum andmaximum distance it is determined if a distribution of said othertouched points in different groups on the basis of their distance isnecessary, if such a distribution is not necessary a weighted average ofthe other touched points is computed and this weighted average issubstituted for the value of the stored image data for the touched pointfor the considered scanning step, if such a distribution is necessarysaid other touched points are distributed in different groups on thebasis of their position and a group is selected according to apredetermined criteria among the different groups, the touched point forthe considered scanning step being determined by a weighted average ofthe other touched points in the selected group.
 27. The method accordingto claim 16, characterized in that the zone of viewpoints is shifted insaid space from a first initial position towards at least a secondposition situated at a predetermined distance of the first position, thescanning by each of the scanners of said first set and the productionand storage of the image data of said space being repeated for eachsecond position of the zone of viewpoints after the one realized for thefirst position.
 28. A visualization method of at least a part of thescanned space on the basis of image data collected according to themethod according to claim 16, characterized in that the method comprisesthe steps of: a) a determination within the zone of viewpoint of aposition and an orientation of the eyes of a user by means of sensorsand the use of an algorithm predicting the head movement of the user,for determining what will be seen by the user; b) a selection on thebasis of the position and orientation of the eyes of the user of imagedata among the stored image data necessary for visualizing of the partof the space which can be seen by the user; c) a loading in a temporarymemory of the selected image data; d) a production of two images on thebasis of the image data stored in the temporary memory; and e) a displayto the user's eyes of the two produced images.
 29. The method accordingto claim 28, characterized in that the display of two images to the useris realized by means of a virtual reality headset.
 30. The methodaccording to claim 28, characterized in that it is used in a device inwhich a movement is conferred to a user, the coordinates of saidconferred movement being sent to a visualization system which appliessaid visualization method for synchronizing the flow of images with saidmovements.